ISO 2568:1988

Overview

ISO 2568:1988 specifies the general dimensions, interchangeability and marking of circular screwing (threading) dies and hand-operated die stocks. Applicable to both hand- and machine-operated circular screwing dies, the standard defines dimensional characteristics tied to thread diameter and pitch and covers a broad set of thread systems used in industry.

Key topics and technical requirements

• Scope of application
  • Applies to ISO metric threads (coarse: M1 to M68; fine: M1 to M56).
  • Applies to ISO inch threads of the Unified family (UNC and UNF): UNC from No. 1‑64 to 2 3/4 ‑ 4; UNF from No. 0‑80 to 1 1/2 ‑ 12.
  • Annex B gives guidance (non‑normative) for non‑ISO inch threads: BSW, BSF, and BA types.
• Dimensional data
  • Specifies general die dimensions as functions of thread diameter and pitch: outside diameter, thickness, cutting portion length, and attachment dimensions.
  • Dimensional tables and cut‑length data are provided (Annex A and main tables).
• Die stocks - interchangeability
  • Defines interchangeability dimensions for hand‑operated die stocks so dies from different manufacturers can fit standard holders (see Table 5 and Figure 3).
• Tolerance and classes
  • Two classes of dies: precision and non‑precision.
  • For precision dies tolerances are specified (example: on D = f10; on E = js12). For non‑precision dies tolerances on D and E are left to the manufacturer’s discretion.
• Marking
  • Clause added in this edition requires dies to be marked with thread designation (examples: "M12 x 1.25", "1/4‑20‑UNC", "No. 12‑28‑UNF", "1/2‑12‑BSW").
  • Manufacturers may append the ISO symbol when fully conformant.

Applications and users

• Manufacturers of threading dies and die stocks who need to design to recognized dimensions and ensure interchangeability.
• Toolmakers, maintenance workshops and metalworking shops choosing or replacing dies for manual or machine threading.
• Purchasing and quality teams specifying tooling to guarantee compatibility across suppliers.
• Technical authors and standards engineers documenting tooling specifications.

Practical benefits

• Ensures interchangeability of dies and die stocks across suppliers.
• Simplifies procurement by standardizing marking and dimensional references for metric and inch threads.
• Facilitates correct selection of precision vs. non‑precision dies based on tolerance requirements.

Related standards

• ISO 2568 references other ISO work (prepared by ISO/TC 29). For taper pipe threads see ISO 4230 (referenced in notes for R‑series threads).